1/*
2 * Copyright (C) 2000, 2001 Jeff Dike (jdike@karaya.com)
3 * Licensed under the GPL
4 */
5
6#include "linux/kernel.h"
7#include "asm/errno.h"
8#include "linux/sched.h"
9#include "linux/mm.h"
10#include "linux/spinlock.h"
11#include "linux/init.h"
12#include "linux/ptrace.h"
13#include "asm/semaphore.h"
14#include "asm/pgtable.h"
15#include "asm/pgalloc.h"
16#include "asm/tlbflush.h"
17#include "asm/a.out.h"
18#include "asm/current.h"
19#include "asm/irq.h"
20#include "sysdep/sigcontext.h"
21#include "kern_util.h"
22#include "as-layout.h"
23#include "arch.h"
24#include "kern.h"
25#include "chan_kern.h"
26#include "mconsole_kern.h"
27#include "mem.h"
28#include "mem_kern.h"
29#include "sysdep/sigcontext.h"
30#include "sysdep/ptrace.h"
31#include "os.h"
32#ifdef CONFIG_MODE_SKAS
33#include "skas.h"
34#endif
35#include "os.h"
36
37/* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by segv(). */
38int handle_page_fault(unsigned long address, unsigned long ip,
39		      int is_write, int is_user, int *code_out)
40{
41	struct mm_struct *mm = current->mm;
42	struct vm_area_struct *vma;
43	pgd_t *pgd;
44	pud_t *pud;
45	pmd_t *pmd;
46	pte_t *pte;
47	int err = -EFAULT;
48
49	*code_out = SEGV_MAPERR;
50
51	/* If the fault was during atomic operation, don't take the fault, just
52	 * fail. */
53	if (in_atomic())
54		goto out_nosemaphore;
55
56	down_read(&mm->mmap_sem);
57	vma = find_vma(mm, address);
58	if(!vma)
59		goto out;
60	else if(vma->vm_start <= address)
61		goto good_area;
62	else if(!(vma->vm_flags & VM_GROWSDOWN))
63		goto out;
64	else if(is_user && !ARCH_IS_STACKGROW(address))
65		goto out;
66	else if(expand_stack(vma, address))
67		goto out;
68
69good_area:
70	*code_out = SEGV_ACCERR;
71	if(is_write && !(vma->vm_flags & VM_WRITE))
72		goto out;
73
74	/* Don't require VM_READ|VM_EXEC for write faults! */
75	if(!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
76		goto out;
77
78	do {
79survive:
80		switch (handle_mm_fault(mm, vma, address, is_write)){
81		case VM_FAULT_MINOR:
82			current->min_flt++;
83			break;
84		case VM_FAULT_MAJOR:
85			current->maj_flt++;
86			break;
87		case VM_FAULT_SIGBUS:
88			err = -EACCES;
89			goto out;
90		case VM_FAULT_OOM:
91			err = -ENOMEM;
92			goto out_of_memory;
93		default:
94			BUG();
95		}
96		pgd = pgd_offset(mm, address);
97		pud = pud_offset(pgd, address);
98		pmd = pmd_offset(pud, address);
99		pte = pte_offset_kernel(pmd, address);
100	} while(!pte_present(*pte));
101	err = 0;
102	/* The below warning was added in place of
103	 *	pte_mkyoung(); if (is_write) pte_mkdirty();
104	 * If it's triggered, we'd see normally a hang here (a clean pte is
105	 * marked read-only to emulate the dirty bit).
106	 * However, the generic code can mark a PTE writable but clean on a
107	 * concurrent read fault, triggering this harmlessly. So comment it out.
108	 */
109	flush_tlb_page(vma, address);
110out:
111	up_read(&mm->mmap_sem);
112out_nosemaphore:
113	return(err);
114
115/*
116 * We ran out of memory, or some other thing happened to us that made
117 * us unable to handle the page fault gracefully.
118 */
119out_of_memory:
120	if (is_init(current)) {
121		up_read(&mm->mmap_sem);
122		yield();
123		down_read(&mm->mmap_sem);
124		goto survive;
125	}
126	goto out;
127}
128
129static void bad_segv(struct faultinfo fi, unsigned long ip)
130{
131	struct siginfo si;
132
133	si.si_signo = SIGSEGV;
134	si.si_code = SEGV_ACCERR;
135	si.si_addr = (void __user *) FAULT_ADDRESS(fi);
136	current->thread.arch.faultinfo = fi;
137	force_sig_info(SIGSEGV, &si, current);
138}
139
140static void segv_handler(int sig, union uml_pt_regs *regs)
141{
142	struct faultinfo * fi = UPT_FAULTINFO(regs);
143
144	if(UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)){
145		bad_segv(*fi, UPT_IP(regs));
146		return;
147	}
148	segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
149}
150
151/*
152 * We give a *copy* of the faultinfo in the regs to segv.
153 * This must be done, since nesting SEGVs could overwrite
154 * the info in the regs. A pointer to the info then would
155 * give us bad data!
156 */
157unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
158		   union uml_pt_regs *regs)
159{
160	struct siginfo si;
161	void *catcher;
162	int err;
163	int is_write = FAULT_WRITE(fi);
164	unsigned long address = FAULT_ADDRESS(fi);
165
166	if(!is_user && (address >= start_vm) && (address < end_vm)){
167		flush_tlb_kernel_vm();
168		return 0;
169	}
170	else if(current->mm == NULL) {
171		show_regs(container_of(regs, struct pt_regs, regs));
172  		panic("Segfault with no mm");
173	}
174
175	if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
176		err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
177	else {
178		err = -EFAULT;
179		/* A thread accessed NULL, we get a fault, but CR2 is invalid.
180		 * This code is used in __do_copy_from_user() of TT mode. */
181		address = 0;
182	}
183
184	catcher = current->thread.fault_catcher;
185	if(!err)
186		return 0;
187	else if(catcher != NULL){
188		current->thread.fault_addr = (void *) address;
189		do_longjmp(catcher, 1);
190	}
191	else if(current->thread.fault_addr != NULL)
192		panic("fault_addr set but no fault catcher");
193	else if(!is_user && arch_fixup(ip, regs))
194		return 0;
195
196	if(!is_user) {
197		show_regs(container_of(regs, struct pt_regs, regs));
198		panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
199		      address, ip);
200	}
201
202	if (err == -EACCES) {
203		si.si_signo = SIGBUS;
204		si.si_errno = 0;
205		si.si_code = BUS_ADRERR;
206		si.si_addr = (void __user *)address;
207		current->thread.arch.faultinfo = fi;
208		force_sig_info(SIGBUS, &si, current);
209	} else if (err == -ENOMEM) {
210		printk("VM: killing process %s\n", current->comm);
211		do_exit(SIGKILL);
212	} else {
213		BUG_ON(err != -EFAULT);
214		si.si_signo = SIGSEGV;
215		si.si_addr = (void __user *) address;
216		current->thread.arch.faultinfo = fi;
217		force_sig_info(SIGSEGV, &si, current);
218	}
219	return 0;
220}
221
222void relay_signal(int sig, union uml_pt_regs *regs)
223{
224	if(arch_handle_signal(sig, regs))
225		return;
226
227	if(!UPT_IS_USER(regs)){
228		if(sig == SIGBUS)
229			printk("Bus error - the host /dev/shm or /tmp mount "
230			       "likely just ran out of space\n");
231		panic("Kernel mode signal %d", sig);
232	}
233
234	current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
235	force_sig(sig, current);
236}
237
238static void bus_handler(int sig, union uml_pt_regs *regs)
239{
240	if(current->thread.fault_catcher != NULL)
241		do_longjmp(current->thread.fault_catcher, 1);
242	else relay_signal(sig, regs);
243}
244
245static void winch(int sig, union uml_pt_regs *regs)
246{
247	do_IRQ(WINCH_IRQ, regs);
248}
249
250const struct kern_handlers handlinfo_kern = {
251	.relay_signal = relay_signal,
252	.winch = winch,
253	.bus_handler = bus_handler,
254	.page_fault = segv_handler,
255	.sigio_handler = sigio_handler,
256	.timer_handler = timer_handler
257};
258
259void trap_init(void)
260{
261}
262